Iranian Journal of Electrical and Electronic Engineering
Volume:3 Issue: 1, Jan 2007

Unlike perfect competitive markets, in oligopoly electricity markets due to strategic producers and transmission constraints GenCos may increase their own profit through strategic biddings. This paper investigates the problem of developing optimal bidding strategies of GenCos considering participants’ market power and transmission constraints. The problem is modeled as a bi-level optimization that at the first level each GenCo maximizes its payoff through strategic bidding and at the second level, in order to consider transmission constraints a system dispatch is accomplished through an OPF problem. The AC power flow model is used for proposed OPF. Here it is assumed that each GenCo uses linear supply function model for its bidding and has information about initial bidding of other competitors. The impact of optimal biddings on market characteristics as well as GenCos’ payoffs are investigated and compared with perfect competitive markets where all the participants bid with their marginal costs. Furthermore, effects of exercising market power due to transmission constraints as well as different biddings of strategic generators on GenCos’ optimal bidding strategies are presented. Finally IEEE-30 bus test system is used for case study to demonstrate simulation results.

From the optimization point of view, an optimum solution of the unit commitment problem with reliability constraints can be achieved when all constraints are simultaneously satisfied rather than sequentially or separately satisfying them. Therefore, the reliability constraints need to be appropriately formulated in terms of the conventional unit commitment variables. In this paper, the reliability-constrained unit commitment problem is formulated in a mixed-integer program format. Both the unit commitment risk and the response risk are taken into account as the probabilistic criteria of the operating reserve requirement. In addition to spinning reserve of generating units, interruptible load is also included as a part of operating reserve. The numerical studies using IEEE-RTS indicate the effectiveness of the proposed formulation. The obtained results are presented and the implementation issues are discussed. Two sensitivity analyses are also fulfilled to illustrate the effects of generating unit failure rates and interruption time of interruptible load.

Transmission loss allocation in very large networks with multiple interconnected areas or countries is investigated in this paper. The main contribution is to propose a method to calculate the amount of losses due to activity of each participant in the multi area markets. Pricing of cross-border trades in Multi area systems is often difficult since individual countries may use incompatible internal transmission pricing regimes, and they are usually unwilling to disclose any sensitive information about their own systems. A new methodology based on the loss formula concept for allocating electric losses to generators and loads is presented in this paper. The only data required are the power flows and characteristics of tie-lines and PV Ward equivalent model of area networks from border nodes point of view. Proposed methodology is tested on the IEEE 118 node network which is divided into three areas, each with a different internal transmission pricing methodology. In the proposed methodology no information is required about individual loads, generations or detailed internal networks. It is also shown to be simple, transparent and very fast and it can deal effectively with multiple pricing policies.

The operation of Fuel Cell Distributed Generation (FCDG) systems in distribution systems is introduced by modeling, controller design, and simulation study of a Solid Oxide Fuel Cell (SOFC) distributed generation (DG) system. The physical model of the fuel cell stack and dynamic models of power conditioning units are described. Then, suitable control architecture based on fuzzy logic control for the overall system is presented in order to active power control and power quality improvement. A MATLAB/Simulink simulation model is developed for the SOFC DG system by combining the individual component models and the controllers designed for the power conditioning units. Simulation results are given to show the overall system performance including active power control and voltage regulation capability of the distribution system.

Because of temperature independence, high resolution and noiseless outputs, brushless resolvers are widely used in high precision control systems. In this paper, at first dynamic performance characteristics of brushless resolver, considering parameters identification are presented. Then a mathematical model based on d-q axis theory is given. This model can be used for studying the dynamic behavior of the resolver and steady state model is obtained by using dynamic model. The main object of this paper is to present an approach to identify electrical and mechanical parameters of a brushless resolver based on DC charge excitation and weight, pulley and belt method, respectively. Finally, the model of resolver based on the obtained parameters is simulated. Experimental results approve the validity of proposed method.